The invention relates to a wagon for carrying a lifting cradle and particularly to the manner of locking in position a load provided with such a lifting cradle, for example a skip, platform, container or the like, on a wagon equipped with pivoting loading structures.
In order to allow movement of a load provided with a lifting cradle between a lorry equipped with a loading/unloading arm and a wagon, it is known to provide on the wagon a rectangular horizontal body connected to the wagon by an articulation having a vertical axis located in the longitudinal plane of symmetry of the wagon and in the longitudinal vertical plane of symmetry of the body, near one of the ends of the body.
In order to load or unload a lifting cradle on the wagon the body must be pivoted laterally to the side where the lorry is located until the body is aligned with the chassis of the lorry. The transfer of the load between the body and the lorry is then performed by maneuvering the loading/unloading arm of the lorry.
If required, conventional means are employed to ensure the compatibility of the height of the chassis of the lorry and of the body.
It should be recalled that the term "lifting cradle" refers to the interfacing elements required to allow the loading/unloading of a load by means of a loading/unloading arm. A lifting cradle principally includes two longitudinal beams, each having at one end a vertical extension at the top of which a holding bar or ring is provided which is adapted to become engaged with the lifting hook of a loading/unloading arm. To this lifting cradle (which is sometimes called a cradle skeleton) is fixed in practice by welding, bolting or the like, the load support proper (plate, box, etc.).
When a lifting cradle is loaded onto a pivotable body from a lorry, the body is brought into alignment with the wagon and the problem which arises is then to lock it in position.
For this purpose it has been arranged to fix to the ends of the longitudinal beams of the body, near which the articulation is mounted, U-shaped stops adapted to receive and arrest rear rollers mounted conventionally on the rear end of the longitudinal beams of the lifting cradle. These stops are adapted to resist unwanted longitudinal forces or forces directed vertically upwards. When the body is brought into alignment with the wagon, the front ends of the longitudinal beams of the lifting cradle (to which the aforementioned vertical extension is fixed) are brought opposite stopping elements fixed to the wagon. In a first embodiment these stopping elements are fixed buffers adapted to resist any longitudinal sliding of the lifting cradle in their direction without any possibility of arresting them if unintended lifting forces occur. In a second embodiment these stopping elements are hooks which become engaged with lateral projections provided at the front of the lifting cradle which are adapted to resist unintended longitudinal or lifting forces.
It is pointed out that the French and European safety standards generally require that the different aforementioned stopping elements must withstand, in the case of accidental collisions, accelerations which may be as large as 4 g.
Despite their merits the aforementioned solutions to the problem have various disadvantages, including in particular the following. When shocks due to stopping are applied to the U-shaped stops provided on the longitudinal beams of the body, all the unwanted forces pass through the intermediary of the body, with consequent risks of damage to the body and to the body/wagon articulation. The sets of stops can only be used for one length of lifting cradle, which means that different wagons must be provided for each type of lifting cradle. Further, it is not possible to load lifting cradles onto the bodies from above.
The object of the invention is to alleviate the aforementioned disadvantages by making it possible to hold, on the body of a wagon, lifting cradles having different lengths, with the wagon directly absorbing the unwanted longitudinal forces in both directions and any lifting forces which might be accidentally applied to the lifting cradles or to the load to which they are fixed, while allowing loading of the lifting cradles from above, without requiring any substantial modifications to the standard geometry of the lifting cradles and with the possibility of adapting existing lifting cradles.